How can I make sure landscape plants I choose are adapted to our climate?
The U.S. Department of Agriculture has developed a climate zone map to help with plant selection. The “Sunset Western Garden Book” has also developed a different climate zone map for Western states. Most nurseries and garden stores in our area use the USDA zones.
We live in a time of warming climate, although you might feel like the opposite is true for this winter and early spring. We are probably two or three weeks behind normal in plant development this year.
The last USDA climate zone map was published in 2012. Plant hardiness zones are based upon the average annual extreme minimum temperature at a specific location. They do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature. Low temperature during the winter is a crucial factor in the survival of plants at specific locations.
The 2012 map includes 13 zones. Each zone is a 10-degree band, further divided in 5-degree zones. Compared to the 1990 map, zone boundaries have shifted in many areas. This is the result of using temperature data from a longer and more recent time period. The new map uses data measured at weather stations during the 30-year period from 1976 to 2005. The new map is generally one 5-degree half-zone warmer than the previous map through most of the United States.
